Very few businesses run entirely online, which means most are going to have offline advertising campaigns, such as TV commercials, radio ads, magazine or newspaper ads, direct mail, fliers, etc. At first glance, it seems difficult to measure ROI for those activities, but there is hope for your campaigns.
Make visiting your website one of your offline calls to action, and you can assign attribution. That approach is actually quite common, but it's often poorly executed.
The tragic mistake is that almost every offline ad refers the user to the homepage. Since that is a direct visit, you can't track who is coming to the homepage because of your ad—or because they already knew about you.
If there is a spike in direct traffic to the homepage, you can estimate that as the impact of an ad campaign but that doesn't help get you solid numbers that you can report on. Furthermore, if you're running multiple campaigns, you can't give credit to the proper campaign.
Setting Up Your Campaigns
To correct that problem, the first step is to send users to a specialized landing page instead of the homepage. We'll call that our ad URL, and in this example we'll use a "www.yourdomain.com/radio-special" as your ad URL. By creating a specialized page, you can see how many people are coming to your site because of your ad.
You need to make sure that people who hear the radio ad remember the URL, though, and don't just conduct on online search for your brand name. This is actually easier than it sounds. If you give incentive to people to remember your ad URL, they will. And nothing works better as an incentive than saving money.
Direct your captive audience to the ad URL ("/radio-special") to receive their special discount that isn't offered anywhere else. That will get their attention, and they will remember your ad URL, not just your brand.
You'll now be able to see how many people are coming to your site because of your ad. Let's take it one step further, though. Let's see how many people are buying from your site because of your offline advertisement.